Four types of oedometer tests (constant rate of strain tests, controlled gradient tests, multiple-stage loading tests and creep tests) were carried out on a variety of Champlain sea clays. Results obtained on five sites are used to demonstrate that the rheological behaviour of these clays is controlled by a unique stress-strain-strain rate relationship. This relationship can be simply described by two curves (σ-p′-ɛv and (σ′/σp′)-ɛv). The significance, the practical implications and the limitations of the model are also discussed. Quatre types d'essais oedométriques (a vitesse constante de déformation, à gradient contrôlé, à chargement en plusieurs étapes et avec fluage) ont été effectués sur diverses argiles marines Champlain. Les résultats obtenus sur cinq sites sont utilisés pour démontrer que le comportement rhéologique de ces argiles est régi par une relation unique contrainte-déformation/vitesse de déformation. Cette relation peut être décrite de façon très simple par deux courbes (σp-ɛv et (σv′/σp′)-ɛv). L'article analyse aussi la signification, les implications pratiques et les limitations du modèle.

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Considering that (i) the hydraulic conductivity of compacted clays is smaller on the wet side of optimum; (ii) the plastic limit is the water content below which the soil develops fissures under small stresses; (iii) the plastic limit and the optimum standard Proctor water content are similar for many natural soils; and (iv) the strength of compacted clays, thus the limit of trafficability, is a function of (w – wopt)/Ip, relevant conditions for the design of clay liners and the evaluation of their hydraulic conductivity are proposed. Key words : compacted clay, liner, hydraulic conductivity, strength, design.

Wear of materials in corrosive environments has received considerable interest in recent years. It has been demonstrated that the wear-corrosion synergy can be markedly affected by the strain rate. In this study, effects of strain rate of prior deformation on corrosion and corrosive wear of AISI 1045 steel in a 3.5 pct NaCl solution were investigated using an electrochemical test, scanning Kelvin probing, and corrosive sliding wear tests, respectively. Six strain rates of prior deformation, from 7.5 · 10 )4 s )1 to 2 s )1 , were employed for this study. In order to understand the mechanism responsible for the effects of the strain rate on corrosion and corrosive wear, worn surfaces, subsurface microstructure, microcracks, and residual strain were examined with scanning electron microscopy (SEM) X-ray line profile analysis. Microhardness tests were also carried out to investigate corresponding changes in mechanical properties of surface layers with respect to the strain rate. Based on the effects of prior strain at different rates on surface microstructure and resultant changes in electrochemical and mechanical properties, the corresponding wear behavior of the steel in the 3.5 pct NaCl solution is discussed.

Stress fields and constraint parameters (Q and A2) of circumferentially-cracked high strength pipe in displacement-controlled tension are compared with those of small-scale single-edge notched samples tested in tension (SE(T)) and bending (SE(B)). The factors affecting transferability of fracture toughness (J-resistance) data from small-scale laboratory tests to cracked high strength pipe are discussed. The crack-tip stress field is of similar form for a circumferential crack in a pipe and a SE(T) test specimen, while for a SE(B) specimen there is a significant gradient in the crack-tip stress field. Hence, the fracture toughness can be characterized by only two parameters (J and Q or J and A2) for tension-loaded pipe and SE(T) tests, but for SE(B) tests one more parameter is needed to describe the bending term. It is concluded that the constraint in a SE(T) test with ratio of span between load points to width H/W = 10 provides a reasonable match to that for a circumferential crack in a pipe subjected to tensile loading.